(1) Field of the Invention
This invention relates to gas generation, and more particularly to gas generation systems useful for fire or explosion suppression purposes.
(2) Description of the Related Art
Rapid deflagrating cord (RDC), sometimes erroneously identified as rapid detonating cord has been in common use in the explosives industry as a transfer line for igniting explosives. Detonating cord (detcord) has been used extensively as a transfer line and as an explosive (e.g., for cutting structural elements). Both RDC and detcord comprise a sheath containing an explosive (commonly identified as a xe2x80x9cpyrotechnicxe2x80x9d in the case of RDC). Detcord typically comprises a plastic or cloth sleeve containing a high explosive charge. When ignited at one end, detcord bums via propagation of a detonating shock wave. The shock wave moves through the explosive at a velocity greater than the speed of sound in the explosive (nearly always in excess of about 2000 m/s and typically 5000-7000 m/s) and ignites the unreacted explosive through which it passes. With RDC, burning is via deflagration, a high velocity subsonic propagation (typically less than 2000 m/s). With RDC, thermal energy is transferred from the reacted explosive to the unreacted explosive primarily via conduction. With detcord and RDC, the combustion involves self-contained oxygen in the explosive charge.
RDC has been used as a component in gas generators. RDC can typically be ignited via the output of a conventional automotive airbag initiator (e.g., one containing a charge of 35 mg zirconium potassium perchlorate (ZPP) or its equivalent). The output of such an initiator is not reliably capable of directly igniting detcord. Detcord requires a detonator to provide the initial energy necessary to induce ignition of the detcord.
U.S. Pat. No. 6,062,143 of Grace et al. identifies a distributed charge inflator (DCI). The application identifies use of an electronic squib (commonly used in automotive airbag inflators) to ignite a core of ignition material such as RDC or mild detonating fuse (MDF). The presence of a gas-generating layer or coating on the core is also identified.
U.S. Pat. No. 5,967,550 of Shirk et al. identifies a staged pyrotechnic air bag inflator. A housing defines a chamber with an end-burning pyrotechnic charge. The charge has a first predetermined burn rate at a first location along the length of the chamber and a different second predetermined burn rate at a second location along the length of the chamber spaced apart from the first location. The second burn rate may be effective to maintain inflation of the air bag over a desired interval.
U.S. Pat. No. 5,224,550 of Bragg identifies an explosion suppression system in which a suppressant is contained within dispersion tubes and is expelled responsive to combustion of an ignition cord.
International Application PCT/US00/30726 (PCT ""726) of Primex Aerospace Company et al. discloses a number of embodiments of a gas generator. The disclosure of PCT/US00/30726 is incorporated by reference herein as if set forth at length. These and other distributed gas generation systems are believed useful in fire suppression. In particular, such systems may be useful in providing a distributed release of fire suppressant.
The suppressant may be in the form of inert combustion gases. The gases may be from charges of primary and secondary propellant-type suppressant agents, for respectively knocking down and sustaining inertion of a fire or explosion. The suppressant may be in the form of a liquid or solid suppressant agent expelled from the extinguisher by an ignition cord.
Key extinguishers have flexible bodies containing at least the primary suppressant. The bodies may extend terminally from a single rigid end fixture or may extend between two end fixtures. An end fixture may contain an initiator and may also contain a secondary sustainer propellant/suppressant charge.
The extinguishers may be deployed and used via various methods. Key methods involve flexing or forming the bodies to conform to a mounting situation and then securing the deformed extinguisher to environmental structure.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.